1. Field of the Invention
The invention is directed to colloidal dampers, smart dampers, magnetic fluid, semi-active vibration control.
2. Description of the Prior Art
The key factor to reduce the durability of current dampers is the failure of rubber materials used for seal purpose. The fundamental mechanism for current state of the art dampers to dissipate external mechanical energy is to convert it into heat. As a consequence, the temperature of current dampers rise very quickly and the dampers are operated at high temperature levels. The higher temperature will derogate rubber materials used in dampers and cause material failure. In addition, temperature change also derogates the damping capacity of damping medium in dampers. Thus, currently either a cooling methodology or high-performance rubber materials are used to improve durability of dampers.
Besides heat generation, current hydraulic dampers possess low damping efficiency, which is defined by the ratio of the dissipated energy per cycle and the input energy during loading phase. The reason is that inner pressure inside the dampers reduces the effective area of damping forces. By theoretical analysis, the efficiency of hydraulic dampers without high pressure nitrogen chambers is
      η    =          1      -                        (                                    D              pr                                      D              p                                )                2              ,where Dpr and Dp are the diameters of piston rods and pistons, respectively. For commercial hydraulic dampers, the rod should have sufficient cross area to transfer damping forces and, therefore, the efficiency for current hydraulic dampers can rarely exceed 50%. To increase damping efficiency, valves with a high pressure drop during loading phase and a low pressure drop during unloading phase are widely used. However, utilization of such valves makes damping curves unsmooth or ragged and increases the fabrication cost of dampers. If a nitrogen chamber is used, damping curves become smooth but damping efficiency becomes even smaller.
Dampers with on-demand controllable damping curves are essential components in an adaptive vibration control system. However, currently, such dampers, e.g., magnetorheological fluid (MRF) dampers, are primarily hydraulic dampers, which dissipate energy by an internal friction mechanism (viscosity) of the fluid passing through orifices. Thus, they also convert all external energy into heat and they have all the above disadvantages of hydraulic dampers.
What is needed is some kind of a damper which is characterized by low heat generation and possesses high damping efficiency without sacrificing the smoothness in the damping curves and has a low fabrication cost. Further what is needed is some kind of a damper in which the damping curves are on-demand controllable, so that such dampers would be material elements in designs which significantly enhance adaptive vibration control systems.